1. Field of the Invention (Technical Field)
The present invention relates to heart compression and assist and arrhythmia control devices. More particularly the invention relates to a multi-soft fingered, resilient electrical heart compression apparatus which can be implanted external to the patient""s heart for compressing a heart ventricle robotically and intelligently, which contains control means such as bradycardic (pacing) and tachyarrhythmic (cardioverting/defibrillating) to facilitate the device operation in synchronism with left ventricular contraction. The apparatus is also preferably capable of transcutaneous recharging of the implanted batteries, or can be powered by a pair of transcutaneous conducting wires by an electronic battery pack system worn around a user""s waist.
2. Background Art
There presently exists no implantable heart compression device to help patients suffering from congestive heart failure (CHF), a progressive disease often precipitated by acute myocardial infarction. All artificial heart or left ventricular assist devices have either not worked in the past or are just temporary solutions for patients needing a donor heart for transplant. Existing devices generally feature blood flow pathways made from non-biological materials that often damage blood cells and blood proteins and produce clots, thereby presenting a generic risk thromboembolism in the circulatory system. In fact, blood clots cause most of the deaths reported after implantation of an artificial heart or assist device. The majority of these patients have a normal right ventricle; however, most have a left ventricle that has been damaged in specific regions. Therefore, there is a need for a heart compression device designed to assist the weak muscles of a failing heart that augments the heart""s pumping power. This device could also incorporate pacemaker and implantable cardioverter/defibrillator technology for treating patients who also suffer from such electrical dysfunctions as bradycardia or tachyarrhythmias. Current Left Ventricular Assist Device (LVAD) devices are heavy and generally have to be attached to a cart to be dragged around by the patient. In addition, they lack a satisfactory implantable energy source, requiring patients to be constantly tethered to an external power source. Previous attempts to provide ventricular assistance have ranged from artificial hearts (e.g., the Jarvik-7), to devices which directly pump the blood, via an artificial pathway inserted through the ventricular wall to devices which exert pressure on the outside of the heart. Historically, heart-compression devices involve some form of flexible bladder within a support structure such that expansion of the bladder presses on the ventricle and facilitates expulsion of blood. These types of devices are disclosed in U.S. Pat. No. 3,587,567 to Schiff; U.S. Pat. No. 3,371,662 to Heid et al.; U.S. Pat. No. 4,048,990 to Goetz; and U.S. Pat. No. 4,192,293 to Asrican. U.S. Pat. No. 4,506,658 to Casile discloses a truncated conical structure of sac-lined rigid panels separated by contractible and expandable sections. Another type of cardiac assist system is designed to compress all or part of the heart by alternately tightening and releasing a circumferential compression band. For example, U.S. Pat. No. 4,304,225 to Freeman teaches the use of a flexible strap which is fixed to a contoured plastic block and which would pass across the back of the heart. In response to electrical pulses, a motor assembly alternately reels in and releases the flexible strap, thereby forcing fluid from the organ. This prior art device is ineffective because a pressure of between 20 and 70 mm Hg in the volume under the strap pumps blood from the right ventricle but not the left, since 70 mm Hg or more is required for blood to exit the left ventricle into the aorta. Freeman also discloses the use of a tubular compression sleeve that substantially encircles the heart and which comprises a series of interconnected expandable elliptical chambers. In use, a liquid solution is pumped into the sleeve from a supply chamber, causing the elliptical chambers to expand radially inward to compress the heart in its systolic phase. The solution then is released from the sleeve back to a supply chamber, permitting the heart to expand in its diastolic phase. These bladder-type devices can lead to a buildup of blood in the lungs, producing pulmonary complications. U.S. Pat. No. 4,583,523 to Kleinke and Freeman illustrates another prior art heart assist mechanism. This device compresses the aorta, not the left ventricle, and it compresses during the diastolic phase of cardiac contraction instead of the systolic phase. There is no means to monitor the adequacy of left ventricular stroke volume.
U.S. Pat. No. 4,925,443 to Marlin S. Heilman and Steve A. Kolenik, discloses an implantable ventricular assist device which includes, (1) one or more movable compression assemblies for engaging a ventricle of the heart; (2) an operating mechanism for cyclically actuating the movable compression assemblies and thereby alternately ejecting blood from the ventricle and permitting the ventricle to refill; (3) a sensing means to detect adequacy of ventricular stroke volume and/or pressure; (4) a control mechanism to assure adequate ventricular stroke volume by regulating the compressive force of the compression assemblies, and also to control pacemaker, cardioverter/defibrillator, and recorder subsystems; and (5) an electrical power source.
To prevent the edges of the compression assembly pressure plates from creating pressure points which might cause possible damage to the heart, a related continuation-in-part patent, U.S. Pat. No. 5,098,369, to Marlin S. Heilman, et al., discloses replacing the contact pad of each compression assembly with a gel-filled contact pad of special construction that compresses the heart ventricle more uniformly without damaging the ventricle. Another related patent, U.S. Pat. No. 5,098,369, to Heilman, et. al., discusses a ventricular assist device for a heart which includes a compression band-stay-pad assembly for encircling substantially the entire heart perimeter and comprising an elongated band member or chain disposed in a sealed protective structure filled with a lubricating medium.
Yet another related patent, U.S. Pat. No. 5,558,617, to Heilman, et. al, discusses a ventricular assist device for a heart including a compression band-stay-pad assembly for encircling substantially the heart perimeter and comprising an elongated band member or chain disposed in a sealed protective structure filled with a lubricating medium. The band member is fixed at one end and wound upon, or unwound from, a rotatable spool by a drive motor through a speed reducer.
Other previous attempts to provide ventricular assistance have ranged from artificial hearts (e.g., the Jarvik-7), to devices which directly pump the blood via an artificial pathway inserted through the ventricular wall, to devices which exert pressure on the outside of the heart. Most frequently, these latter pressure-exerting devices involve some form of flexible bladder within a support structure such that expansion of the bladder presses on the ventricle and facilitates expulsion of blood. These types of devices are disclosed in U.S. Pat. No. 3,233,607 to Bolie; U.S. Pat. No. 3,279,464 to Kline; U.S. Pat. No. 3,587,567 to Schiff; U.S. Pat. No. 3,371,662 to Heid et al.; U.S. Pat. No. 4,048,990 to Goetz; U.S. Pat. No. 4,192,293 to Asrican; U.S. Pat. No. 3,455,298 to Anstadt; U.S. Pat. No. 4,690,134 to Snyder; U.S. Pat. No. 5,169,381 to Snyder; U.S. Pat. No. 5,256,132 to Snyder; U.S. Pat. No. 4,731,076 to Noon et al.; and U.S. Pat. No. 4,957,477 to Lundbxc3xa4ack. U.S. Pat. No. 4,506,658 to Casile discloses a truncated conical structure of sac-lined rigid panels separated by contractible and expandable sections. U.S. Pat. No. 4,621,617 to Sharma shows another similar device which is electromagnetically controlled and comprises a pair of hinged compression members. Further, U.S. Pat. No. 4,536,893 to Parravicini teaches using two segmented sacs, selectively fed by a pumping fluid to compress the right and left ventricles separately. In general, bladder systems have various shortcomings. These include the possibility of catastrophic bladder fluid leakage (as a result of the fluid pressures involved), a propensity for damaging the heart surface due to poor fixation and/or rubbing of the bladder against the heart""s surface, and the unnatural convex form presented to the heart""s surface during systolic bladder expansion. U.S. Pat. No. 4,583,523 to Kleinke and Freeman illustrates a heart assist mechanism that compresses the aorta, rather than a ventricle, and it compresses during the diastolic phase of cardiac contraction instead of the systolic phase.
Other prior art references of relevance to the present invention are:
U.S. Pat. No. 5,250,167 to Adolf, et al., and U.S. Pat. No. 5,389,222 to Shahinpoor in connection with electrically controllable polymeric actuators;
Y. Wakisaka, et al., xe2x80x9cApplication of Hydrogen Absorbing Alloys to Medical and Rehabilitation Equipmentxe2x80x9d, IEEE Trans. on Rehabilitation Engineering, Vol. 5, No. 2, pp. 148-157 (1997);
M. Shahinpoor, xe2x80x9cIonic Polymer Metal Composition as Biomimetic Sensors and Actuatorsxe2x80x9d, in Polymer Sensors and Actuators, edited by Y. Osada and D. DeRossii, Springer-Verlag Publishing, Springer (1999); and
M. Shahinpoor, Y. Bar-Cohen, J. O. Simpson, J. Smith, xe2x80x9cIonic Polymer Metal Composites (IPMC""s) as Biomimetic Sensors, Actuators and Artificial Musclesxe2x80x94a Reviewxe2x80x9d, J. Smart Mater Structures, Vol. 7, pp 15-30 (1998).
This invention comprises an implantable and entirely electrically-controlled external heart compression apparatus in the form of soft, multi-fingered resilient robotic hands for selectively assisting the ventricles, and in particular the left ventricle, of a weak heart to produce more internal pressure and to pump blood from one or more sides in synchrony with the natural systolic contraction of the ventricle. In addition, a number of methods for externally compressing a heart is included. The preferred apparatus also provides arrhythmia control of the beating heart and is powered by a robotic solenoid actuator or similar robotic actuation mechanism, including robotic metal hydride actuators as well as electroactive polymeric artificial muscles. Each of these apparatuses is for cyclically actuating the resilient compression soft fingers, thereby cyclically pumping blood from the ventricles and allowing the ventricles to refill. These apparatuses are completely implantable in the body of a patient external of the heart, thereby avoiding thrombogenesis and other complications that may arise from contact between the blood flow and artificial, nonbiological surfaces. The plurality of soft fingers comprise suitably located electrodes for heart monitoring purposes to determine the ventricular stroke volume and/or pressure. Specifically, the apparatus provides for an entirely electrically-controllable and micro-processor-controlled multi-fingered resilient sphinctering heart-compression that can be implanted inside the ribcage of a patient with a weak heart and gently squeeze the weak heart (systole) to enhance blood circulation and assist the weak heart. These apparatuses are comprised of a specially designed assembly of soft fingers that work in harmony, by means of a micro-processor controlled solenoid or other linear robotic actuators, and a resilient body or a spring, to close once the robotic solenoid is powered electrically. The apparatus is designed to be normally open (not compressing) when there is no power to the robotic solenoid or actuator. The assembly is spring loaded so that when power is removed, the fingers immediately spring open. This apparatus operates like the fingers of a hand to squeeze a weak heart (systole) but otherwise to quickly retract and stay open and away from the heart in an idle manner if the robotic actuation means is not powered. This quick opening action allows the heart to expand freely (diastole) once it is compressed to allow the blood to naturally and freely return to the heart ventricles and coronary veins. External pressure by the myocardium during ventricular systole compresses the heart muscle (myocardium) and decreases blood flow to the coronary veins that feed the heart even though the aortic pressure is increased. Thus, more than 70 percent of the coronary arterial flow occurs during diastole. The multi-fingered configuration may also have the soft fingers connected to each other by elastic membranes, bladders or skirts to provide a resilient, multi-fingered compression cup as well. In one embodiment of the invention the multi-fingered compression apparatus is equipped with a long slender and flexible and undulating stem connecting the multi-fingered compression structure to the robotic actuation mechanism housed in the abdomen of the patient. In another embodiment of the invention, an assembly of electroactive polymer fingers or patches are sutured to the myocardium and are directly electrically flexed to squeeze the heart. Yet in another embodiment of the invention, an assembly of bladder-like fingers is inflated by hydrogen gas from an electrically controlled metal-hydride actuator to create compression of the heart. The preferred embodiment of robotic actuator is a solenoid for its quick action and retraction. However, alternatively, linear motors or robotic actuators as well as robotic metal hydride actuators and polymeric artificial muscles can also be used. The power supply for the implanted apparatus can be long lasting batteries that can be recharged transcutaneously, and various other components of the apparatus can be noninvasively computer-programmed and interrogated by external circuits. The entire apparatus can be implanted endoscopically or through the abdomen of the patient rather than opening of the patient""s chest. The power and electronic control means may also be placed outside the body, around the waist of the person, and directly connected by means of conducting wires through sutured conduits to the implanted apparatus.
A primary object of the present invention is to provide a weak heart, a family of new heart assist devices that are robotically computer controllable and implantable in the patient""s body external to the heart, that are further, compact and light-weight.
A further object of the invention is to provide selective compression of different parts of the heart or thoracic aorta in synchrony and harmony with the natural systolic and diastolic motions of the heart.
Yet another object of the present invention is to provide an endoscopically implantable selective heart compression device equipped with built-in robotic metal hydride actuators that are electronically computer controllable.
Yet another object of the present invention is to provide an endoscopically implantable selective heart compression device equipped with robotic electroactive polymeric muscles that are electrically computer controllable.
A primary advantage of the present invention is to provide selective compression of different parts of the heart and thoracic aorta by means of specially contoured soft resilient fingers.
Yet another advantage of the present invention is to provide the heart with complete lateral and twist motions, while engaged in compression of the weak heart, by means of a flexible stem.
A further advantage of the present invention is to provide a patient with a weak heart an totally endoscopically implantable, multi-fingered compression device equipped with built-in metal hydride actuators for pneumatic computer-controlled compression of the heart.
Yet another advantage of the present invention is to provide a patient with a weak heart an endoscopically implantable, multi-fingered compression device equipped with electroactive polymeric artificial muscles which are robotically computer controllable.
Other objects, advantage and novel features, and further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.